This invention relates to a weight change indicating apparatus. More particularly, this invention relates to an apparatus and method for indicating moisture level changes in soil of a potted houseplant and providing a guide to water and restore proper moisture level in the soil.
It is well known that proper soil moisture level is critical for maintaining healthy growth of potted houseplants. To keep the soil moist, a common practice is to water houseplants weekly or biweekly. However, the change of soil moisture level at regular time intervals may vary significantly due to the variation in atmospheric conditions such as temperature and humidity. Therefore it is usually difficult to estimate how much water should be added for restoring proper soil moisture level. Either overwatering or underwatering may prevent the houseplant from reaching its potential and even shorten the life of the houseplant.
A variety of devices have been developed for monitoring soil moisture level of potted houseplants. Most devices use sensing probes for monitoring soil moisture level. For example, U.S. Pat. No. 4,020,417 to Brehob et al, U.S. Pat. No. 4,514,722 to Batcheler et al, U.S. Pat. No. 6,198,398 to Velasquez, U.S. Pat. No. 6,202,479 to Frybarger and U.S. Pat. No. 6,700,395 to Perry, all disclose different moisture sensing probes which can alert caretakers when the soil is too dry or too wet. However, the uses of these devices have several disadvantages. These devices may be dimensioned to penetrate the full depth of the soil to give an indication of the soil moisture level. Repeatedly inserting probes may hurt roots. Moreover, the moisture level at top, middle, and bottom layer of the soil may be different. But the soil moisture levels detected by the probes are confined to the area where the probes are located. Moreover, probes of these types may malfunction due to a buildup of foreign matter on, or corrosion of, the metal probe surface which contacts the soil. Finally, these devices are usually set to sense a pre-determined low or high moisture level and trigger a visual or audible signal. Before the soil moisture level reaches to the threshold, these devices cannot indicate the actual changes of water content in the soil.
Other methods have also been proposed for monitoring soil moisture level by sensing weight change in the soil of the potted houseplant. For example, U.S. Pat. No. 5,079,869 to Dawson, U.S. Pat. No. 5,802,764 to Nucci, and U.S. Pat. No. 6,564,509 to Zahner, all disclosed a weight-responsive device for indicating changes in weight of a suspended pot holding houseplants. However, these devices are designed only for suspended houseplants. U.S. Pat. No. 6,295,865 to Cherry discloses an electronic device with a processor and a power supply for monitoring weight change of a potted houseplant. However, the processor and other electronic components used in the device are complicated and expensive, thus represent a significant financial investment.